2009_Book_FoodChemistry

628 13 Fish, Whales, Crustaceans, Mollusks
Table 13.9. Minerals in fish muscle
Element Content Element Content
(mg/kg)
(mg/kg)
Ca 48–420 Fe 5–248
Mg 240–310 Cu 0.4–1.7
P 1730–2170 I 0.1–1.0
oxidatively active tocopherols is relatively low.
Therefore, the lipids of fish represents a major
problem in preservation because of its easy peroxidation
(cf. 13.1.4.8).
13.1.4.6 Vitamins
Fish fat and liver (liver oil) are significant sources
of fat-soluble vitamins, A and D. Also present are
vitamins E (tocopherol) and K. The water-soluble
vitamins, thiamine, riboflavin and niacin, occur in
relatively high amounts, while others are present
only in low amounts.
13.1.4.7 Minerals
The average content of major minerals in fish
muscle tissue is compiled in Table 13.9.
13.1.4.8 Aroma Substances
Aroma substances are formed by the enzymatic
oxidative degradation of the highly unsaturated
fatty acids with the participation of lipoxygenases
of varying specificity. These aroma substances
contribute to the mild green-metallic-mushroom
aroma of fresh fish. Dilution analyses have
shown that these substances are acetaldehyde,
propanal, 1-octen-3-one, (Z)-1,5-octadien-3-one,
(E,Z)-2,6-nonadienal, (Z,Z)-3,6-nonadienal and
(E,E)-2,4-decadienal.
Using salmon as an example, Table 13.10 (compare
LO with LI) shows how the concentrations
of important odorants change in the cooking process.
The highly volatile substances acetaldehyde
and propanal decrease and hexanal, (Z)-4-hep-
Table 13.10. Influence of the storage temperature of the raw material on the formation of odorants during cooking
of salmon and cod a
Aroma substance Salmon Cod
LO b LI c LII c KI c KII c
Acetaldehyde 3700 2300 2500 1300 2400
Propanal 3500 1700 4700 n.a. n.a.
2,3-Butandione 57 52 n.a. 200 596
2,3-Pentandione 141 234 318 86 26
Hexanal 35 58 148 n.a. 28
(Z)-3-Hexenal 2.6 3.9 50 1.3 4.3
(Z)-4-Heptenal 3.0 6.0 47 1.6 2.8
Methional 3.0 8.0 4.4 11 10
1-Octen-3-one 0.5 0.4 0.4 0.7 0.2
(Z)-1,5-Octadien-3-one 0.4 0.3 0.5 0.1 0.16
(Z,Z)-3,6-Nonadienal n.a. 5.7 49 1.3 4.2
(E,Z)-2,6-Nonadienal 9.3 9.7 26 3.5 2.8
(E)-2-Nonenal 2.0 2.7 6.4 n.a. n.a.
(E,E)-2,4-Nonadienal 2.2 2.6 3.7 3.2 2.0
(E,E)-2,4-Decadienal 4.8 6.0 18 3.5 2.2
Methanethiol n.a. n.a. n.a. 100 130
2-Methylbutanal n.a. n.a. n.a. 20 270
3-Methylbutanal n.a. n.a. n.a. 51 620
a Concentrations given in µg/kg raw or cooked fish; n.a.: not analyzed.
b LO: raw salmon (Salmo salar), stored for 14 weeks at −60 ◦ C.
c Salmon and cod (Gadus morhua) were each stored for 14 weeks at −60 ◦ C(LI,KI)and−13 ◦ C (LII, KII), then
covered with aluminium foil and heated in a boiling water bath for 15 min.